function radians n
    return n * (3.1415926 / 180)
end radians

function haversine lat1, lng1, lat2, lng2
    local radiusEarth
    local lat3, lng3
    local lat1Rad, lat2Rad, lat3Rad
    local lngRad1, lngRad2, lngRad3
    local haver
    put 6372.8 into radiusEarth
    put (lat2 - lat1) into lat3
    put (lng2 - lng1) into lng3
    put radians(lat1) into lat1Rad
    put radians(lat2) into lat2Rad
    put radians(lat3) into lat3Rad
    put radians(lng1) into lngRad1
    put radians(lng2) into lngRad2
    put radians(lng3) into lngRad3

    put (sin(lat3Rad/2.0)^2) + (cos(lat1Rad)) \
          * (cos(lat2Rad)) \
          * (sin(lngRad3/2.0)^2) \
          into haver 
    return (radiusEarth * (2.0 * asin(sqrt(haver))))

end haversine